1. Field of Invention
This invention relates generally to a combustion chamber in an internal combustion engine, and more particularly to providing a multizone combustion chamber in a compression-ignited engine such as, for example, a diesel engine, or a homogeneous charge compression ignition engine (HCCI).
2. Description of Related Art
One type of internal combustion engine is a diesel engine. During operation, air is drawn into a cylinder of the engine and is compressed to a high volume ratio (typically 14:1 to 25:1). As a result, a high temperature of between about 300xc2x0 C. and 400xc2x0 C. is obtained. Fuel is not injected into the cylinder until the end of the compression stroke. Because of the high temperature of the air, the fuel ignites spontaneously. However, ignition does not take place immediately after the fuel is injected. The fuel enters the cylinder in the form of liquid droplets. These droplets must mix intimately with the air in the cylinder and vaporize before they can ignite to commence combustion. This inherent delay in combustion renders the combustion process a relatively slow process which is not conducive to complete mixture of fuel, thereby limiting the efficient operation of the diesel engine to relatively low speeds and causing the engine to smoke.
U.S. Pat. No. 2,234,844 to Mitchell, the entire disclosure of which is incorporated herein by reference, discloses a dual chamber combustion chamber segregated by a piston motion, yet allowing pressure equilibrium as the piston approaches top dead center (TDC). Mitchell does not disclose initiating combustion in a primary chamber and delaying combustion in the secondary chamber.
U.S. Pat. No. 4,164,915 to Kulhavy et al., the entire disclosure of which is incorporated herein by reference, discloses a method for converting a gasoline engine to a diesel engine. A piston is provided with a projection that segregates the chamber into two chambers. High velocity flows from a high-pressure chamber to a low-pressure chamber. Kulhavy et al. also does not teach initially combusting in a primary chamber and delaying combustion in a secondary chamber.
U.S. Pat. No. 3,386,422 to Eyzat, the entire disclosure of which is incorporated herein by reference, discloses a compression-ignition engine having a piston projection that forms a variable cross-sectional prechamber flame-jet combustion and increased turbulence. Eyzat also fails to disclose initiating combustion in a primary chamber and delaying combustion in the secondary chamber.
U.S. Pat. No. 2,696,808 to Chronic et al., the entire disclosure of which is incorporated herein by reference, discloses a turbulence chamber for internal-combustion engines having a piston with a projection and a head with a receiver. The combustion chambers are eccentric cylindrical chambers with fuel injection and energy (pre-chamber) targeted for increased turbulent motion. Chronic et al. also does not disclose initiating combustion in a primary chamber and delaying combustion in the secondary chamber.
U.S. Pat. No. 6,119,650 to Tanigawa et al., the entire disclosure of which is incorporated herein by reference, discloses an energy conservation cycle engine having dual chambers with piston projections and head receivers from two chambers at TDC. One-way check valves are provided to allow communication between chambers from a second outer chamber to a first inner chamber. The check valves permit compressed air in the second chamber to be injected into the first chamber during the compression stroke. The fuel is only injected into the first chamber. Tanigawa et al. does not disclose controlling HCCI combustion or the resulting decrease in NOx due to peak temperature control. Further, Tanigawa et al. does not form an air/fuel mixture in the second chamber prior to combustion.
It is desirable to provide a multizone combustion chamber that physically segregates the combustion chamber into multiple smaller chambers where at least one of the multiple chambers is a primary combustion chamber. The multizone combustion chamber promotes an increase in the mixture and vaporization of the injected fuel. The multizone combustion chamber also provides different effective compression ratios during the ignition and/or combustion of a reciprocating engine thereby assisting in the control of the combustion process and a reduction in NOx. Segregation of the chambers is obtained when the piston has been moved to a predetermined position that causes the chambers to be sealed off from fluidly communicating with each other. The increased control of the combustion process effectively reduces conventional limits on the efficient operation of the internal combustion engine.
This invention has been made in view of the above circumstances. The present invention addresses the long-standing problems discussed above by providing a multizone combustion chamber and a method for controlling combustion in an internal combustion engine which operate to bring about a desired performance in speed, power output, fuel consumption and exhaust emission of the engine system. Better fuel consumption and reduced emission is obtained because the multizone combustion segregates a combustion chamber into multiple chambers and stages for combustion, thereby fostering homogeneous mixing of fuel with air before the air-fuel mixture is ignited by compression.
One aspect of this invention is to provide a multizone combustion chamber in an internal combustion engine. The multizone combustion chamber includes a cylinder, a cylinder head located at one end of the cylinder, a piston that reciprocates in the cylinder, and an inlet that supplies fuel, air or a combination thereof into the combustion chamber during an induction stroke of the piston. Additionally, an injector may be included that supplies a fuel directly into the combustion chamber. The combustion chamber defines a primary chamber and a secondary chamber when the piston has been moved to a predetermined position near the cylinder head. The primary and secondary chambers contain respective mixtures of the gas and the fuel prior to combustion. The primary and secondary chambers are sized such that compression combustion is initiated in the primary chamber by compression of the gas/fuel mixture therein, while simultaneous initiation of compression combustion does not occur in the secondary chamber due to compression of the gas/fuel mixture in the secondary chamber.
Another aspect of this invention is to provide a method for combustion in an internal combustion engine having a combustion chamber. The multizone combustion chamber includes a cylinder, a cylinder head located at one end of the cylinder, a piston that reciprocates in the cylinder, and an inlet that supplies fuel, air or a combination thereof into the combustion chamber during an induction stroke of the piston. Additionally, an injector may be included that supplies a fuel directly into the combustion chamber. The method comprises: (1) segregating the combustion chamber into at least two sub-chambers when the piston has moved to a predetermined position near the cylinder head, (2) initiating compression ignited combustion in one of the sub-chambers that has been sealed off from an adjacent sub-chamber, and (3) initiating compression ignited or assisted combustion in the adjacent sub-chamber after segregation of those two sub-chambers has been eliminated.